THE former Australian Prime Minister Paul Keating was, infamously, no wallflower in parliamentary debate, routinely describing his opponents as "brain-damaged", "scumbags" and "maggots".

Alas, our MSPs are denied such delicacies.

Whenever any of them starts being entertainingly offensive, Presiding Officer Tricia Marwick directs a nicotine-stewed bark at them for "unparliamentary language".

At FMQs, she was on a hair trigger.

She should have called out Johann Lamont and Alex Salmond for failing to speak English as they traded incomprehensible numbers as part of their weekly war over the White Paper.

But instead of nicking those two, Ms Marwick turned her crabbit fire on Ruth Davidson.

The Tory leader had brandished an opinion from Euro-boffin Jean-Claude Piris saying the SNP plan for EU entry in the event of a Yes vote was a non-starter, with the emphasis on the Non.

As is traditional, the FM ignored the point and tried to talk about something else.

In this case, "an impeccable source, the guru of the Better Together campaign, professor Jim Gallagher", who had said fast entry was likely.

Ms Davidson was undeterred: "The First Minister misled the Scottish public on EU legal advice-" "Orrrder!" rasped the PO. "Ms Davidson, can we withdraw?"

Ms Davidson could not have looked more stunned if her party had acquired a second MP.

"That had previously been ruled on .. and was admitted," she stuttered.

"Whit was wrong with that?" added the indignant fruity twang of Tory deputy Jackson Carlaw.

Shrugging theatrically, Ms Davidson niftily changed tack while getting her revenge.

"I will correct the record by saying the First Minister was unadjacent to the truth."

Mr Salmond responded with an equally nippy "I know it's difficult for Jim Gallagher to be caught telling the truth ..."

On a point of order, Labour's Neil Findlay later asked if "misled" and "misleading" should have been banned, as they regularly escaped censure on other days.

"There are no set guidelines on what is or is not parliamentary language," said Ms Marwick. "The judge (sic) on any particular occasion is mine."

At which MSPs departed muttering some extremely unparliamentary language under their breath.